This invention relates to an apparatus for exchanging die assemblies of a plurality of kinds for an extruder for a short period of time.
Apparatus for exchanging dies assemblies for extruders have been known, for example, as disclosed in Japanese Patent Application Laid-open No. 61-44,618. The apparatus disclosed in the Laid-open application comprises a die holder arranged on an extruding side of an extruder and extending in a first direction perpendicular to an extruding direction (vertical direction) and in parallel with a horizontal, a hydraulic cylinder for moving the die holder in the first direction, two die assembly loading units provided on the die holder and spaced apart from each other in the first direction, and a lifting jack for moving the die holder in a second direction in parallel with the extruding direction.
In an exchanging die assembly with such apparatus, the following steps are effected. It is assumed that a die assembly located on the one die assembly loading unit is mounted on a delivery opening of the extruder and a material is being extruded through the die assembly. A die assembly to be next used is loaded on the other die assembly loading unit. When the extruding operation is completed under such a condition, the die assembly is released from the extruder. At the same time, the lifting jack is operated to move the die holder in the second direction away from the extruder. As a result, the used die assembly is arranged on the one die assembly loading unit. As the die holder is pressed to the extruder by the lifting jack during the extrusion of the material, time loss is less and operation efficiency is improved in comparison with a case where the die assembly is retracted from the extruding position after the die holder is separated from the die assembly.
Thereafter, the die holder is moved in the first direction by means of the hydraulic cylinder so that the die assembly on the one die assembly loading unit is moved to an exchanging position and the die assembly on the other die assembly loading unit is moved to a position in opposition to the delivery opening of the extruder. The lifting jack is then actuated to move the die holder in the second direction to press the die assembly against the extruder, while the die assembly is clamped to the extruder by clamp means. In this case, the used die assembly on the other die assembly loading unit is exchanged with a die assembly to be next used by an operator or die assembly storing and supplying means.
With the die assembly exchanging apparatus for the extruder above described, however, the die older cuts the extruded material on the way of the operation, if the die holder is moved in the first direction during operation. It is, therefore, required to fix the die holder at a predetermined position, so that positions where the die assemblies are exchanged are limited only to one or two. As a result, in the event that die assemblies of three or more kinds are exchanged, a die assembly storing and supplying apparatus such as a rotary index or the like is needed. Therefore, the apparatus becomes bulky and expensive as a whole. It may be possible to exchange the die assemblies by an operator using a crane or the like without using the die assembly storing and supplying apparatus. However, such an operation with the crane is dangerous and hard labor.